Star dust brought to Earth originated beyond our solar system

This illustration shows NASA's Stardust space probe, launched nearly five years ago, which is due to capture the first-ever samples of comet dust. (AFP Photo / NASA) / AFP

​NASA’s Stardust robotic mission which gathered samples from the flyby comet Wild 2 and brought them to Earth in 2006 has proven to be a success, with scientists saying some particles it collected originated from outside our solar system.

“They are very precious particles,” physicist Andrew
Westphal of the University of California, Berkeley said in a
Thursday statement. Westphal has been leading the research ever
since the samples were delivered to Earth eight years ago.

So far seven microscopic particles collected from Stardust
aerogel traps are likely to be first samples of interstellar dust
delivered on Earth for research – and 30,000 volunteer
citizen-scientists dubbed “dusters” of the Stardust@home project are still examining the
optical microscope image scans of aerogel in search of more
stardust.

“The numbers and sizes of dust grains were not what we'd
expected, and many seemed to have come from strange
directions,” Anton Kearsley, a microanalyst who took part in
the study at the Natural History Museum in London, told The
Guardian. “Only by careful plotting of impact directions was
the team able to identify the seven particles that must have come
from outside the solar system,” he said.

The Stardust comet-chaser was launched back in 1999 to collect
dust from the tail of Comet Wild-2. Seven years later the
Stardust capsule successfully landed by parachute in the Utah
desert, USA.

Westphal said the particles look very different from each other,
as some of them resemble fluffy snowflakes while others were
broken up or even vaporized due to their high speed, up to 15
kilometer per second, when they hit the gel traps.

Four other particles got stuck in thin aluminum foils built into
the detectors, Rhonda Stroud at the Naval Research Laboratory in
Washington DC told The Guardian. “They were splattered a bit,
but the majority of the particles were still there at the bottom
of the crater,” she said.

The scientist revealed that the two largest recovered particles
contain olivine, a crystalline magnesium-iron-silicate mineral
that forms in the discs around stars.

“We seem to be getting our first glimpse of the surprising
diversity of interstellar dust particles, which is impossible to
explore through astronomical observations alone,” Westphal
said.

Yet even the biggest samples of interstellar dust are thousandths
of a millimeter across and weigh mere millionths of a millionth
of a gram.

Two particles that left distinct traces in the aerogel were given
proper names, Orion and Hylabrook.

The particles found so far could be considered ‘young’ by space
standards, no older than 100 million years old or even younger
than 50 million years.

The aerogel traps captured both cometary and interstellar dust,
yet for scientists the latter presents much more interest as such
particles could be remnants of supernova stars that exploded
millions of years ago.